A user of a client device relies on one or more dictionaries of words for spell checking, suggesting words during typing, and other uses of known words. Such client dictionaries are difficult to keep updated with new words that may become popular through crowdsourced usage of words without compromising privacy.
Current servers can learn the words that users are typing by examining clear text that users have typed when utilizing the servers. For example, some prior art text message services and email services (collectively, messages) receive messages in clear text. Message servers that route messages to client devices can read the clear text and use the words obtained from the clear text of user messages to present advertising to the users. However, the server-learned words remain on the server and do not update an on-device dictionary to include the new words. Also, usage of clear text by servers compromises the privacy of a user. In addition, new words generated on a client device, such as words that are used within documents on the client device and are not transmitted to a server, cannot be learned by the server because the words are localized to the client device. Further, if the client device utilizes an end-to-end encrypted messaging service, such as Apple® iMessage, then a server cannot learn the words contained in the user message at all and thus a server cannot update a user client dictionary using crowdsourced data.